This invention relates to a method and apparatus for managing the temperature of a hydraulic pump that uses an electric motor.
In aircraft and other applications, electrical motor driven pumps are used to provide or supplement hydraulic power for actuators and other hydraulically or fluid powered components. In many cases, these pumps are inactive for long periods in cold environments and then are expected to startup rapidly and provide full performance in a very short period of time.
In cold environments, the hydraulic fluid becomes very viscous so that starting the pump under sustained cold conditions is difficult. To decrease the viscosity of the fluid and enable desired startup of the pump, it is typical to either run the pump continuously or to provide the pump with a continuous flow of hot gases, typically bleed air from a turbine engine. Continuously running the pump decreases the life of it and the electric motor. Providing a continuous flow of bleed air decreases the efficiency of the source providing the bleed air.
To avoid the above problems, power sufficient to provide a stall torque to the electric motor has been used to generate heat using the windings of the electric motor. Similar to the solutions described above, the power is provided to the electric motor continuously, which is inefficient. What is needed is an efficient hydraulic pump and electric motor system that reduces the viscosity of the hydraulic fluid on an as-needed basis.